Unit Testing and Analysis Using a Stored Reference Signal

ABSTRACT

Method and system for a test process. The method may include performing tests on one or more units under test (UUTs). At least one test on one or more UUTs may be performed. A signal may be acquired from the UUT. A reference signal may be retrieved. The reference signal may be derived from a transmitted signal characteristic of the UUT. The signal may be analyzed with respect to the reference signal. Results, useable to characterize the one or more UUTs, from performing the at least one test on the one or more UUTs may be stored. The reference signal may be derived from an initial test and may be stored for subsequent retrieval. A respective reference signal may be retrieved for all UUTs of the one or more UUTs for a respective test. The signal may be a radio frequency signal. The UUT may be a wireless mobile device.

FIELD OF THE INVENTION

The present invention relates to the field of unit testing, and morespecifically, to a system and method for performing tests, e.g., radiofrequency tests, on units under test using a stored reference signal.

DESCRIPTION OF THE RELATED ART

To ensure reliable performance of a product, quality control has becomea major part of manufacturing. Therefore, each unit manufactured istested under a number of conditions to ensure quality. Each test mayrequire a number of instruments to perform a measurement and based onthe outcome of this measurement, a decision is made to mark the unit aspass or fail. Hence, manufacturing testing plays an important role inensuring quality products in the marketplace. Additionally, the cost ofrunning quality control tests in a manufacturing environment directlyrelates to the cost of products in the market place and a manufacturer'sprofit. The cost of testing can be further magnified in large quantityproduction facilities where each unit must pass a quality control test.In such instances, the most significant cost of running the qualitycontrol test is the time it takes to run each test.

In the radio frequency (RF) domain, these quality control measurementsare complex and may take a substantial amount of time. The measurementsare generally taken by a signal analyzer (SA). A flowchart for a typicalmethod for performing a measurement is illustrated in FIG. 1. It shouldbe noted that measurement 200 is typically performed multiple times foreach unit under test (UUT). In 202, a signal, x(n), is acquired. Thesignal may be acquired by a SA. In 204, the distortions from theacquired signal are removed creating the reference signal, r(n). In somecases, removing the distortion to create the reference signal, r(n), mayinvolve demodulating, including hard decision demodulating, andre-modulating the signal. In other cases, only demodulation, includinghard decision demodulation, may be necessary. In either case, the signalprocessing required to create the reference signal is time intensive. In206, any of various signal processing functions, including removingdistortions from the signal x(n) using the reference signal, r(n), maybe performed that compare and correlate the reference signal to theacquired signal, thereby resulting in a metric that measures theperformance of the UUT. As mentioned, the measurement is repeatednumerous times. Hence, any method that decreases the testing orprocessing time of the signal, will improve test throughput, therebyreducing testing time and manufacturing cost.

The basic method illustrated in FIG. 1 may be applied to severalmeasurements when analyzing the RF signals for non-OrthogonalFrequency-Division Multiplexing (non-OFDM) cellular standards, such asWideband Code Division Multiple Access (WCDMA), and the Code DivisionMultiple Access 2000 family of standards (CDMA2K). It may also beextended for measurements on OFDM cellular standards such as GlobalSystem for Mobile Communications—Enhanced Data rates for GSM Evolution(GSM-EDGE), Long Term Evolution (LTE), Worldwide Interoperability forMicrowave Access (WiMAX), and Wireless Local Area Network (WiLan).Further, it may be extended for Time Division Multiple Access (TDMA)cellular standards, such as Global System for Mobile Communication(GSM). Typically, the metrics computed in 206 include Error VectorMagnitude (EVM), Modulation Accuracy EVM, Code Domain Power, EVMQuadrature Phase-Shift Keying (EVMQPSK), and so forth.

SUMMARY OF THE INVENTION

Embodiments of the present invention relate to systems and associatedmethods for performing a test process. In one embodiment, a method mayutilize a computer to implement performing at least one test on one ormore unit under tests (UUTs). A signal may be acquired from a UUT of theone or more UUTs. A reference signal may be retrieved, where thereference signal is derived from a transmitted signal that ischaracteristic of the UUT. The signal may be analyzed with respect tothe reference signal. The results of the performance of the at least onetest on the one or more UUTs may be stored. The results may be useableto characterize the one or more UUTs. In some embodiments, performing atleast one test on the one or more UUTs may include performing at leastone radio frequency (RF) test on at least one mobile wireless device.

In one embodiment, a marker may be used to synchronize the acquiring ofthe signal with the reference signal. In various embodiments, the markermay include a digital pulse, a software trigger, a power edge trigger,or a correlation method, e.g., a cross-correlation technique, or otherform of signal synchronization. In some embodiments where the marker isa digital pulse, the acquiring of the signal may be initiated by an edgeof the digital pulse, e.g., may be used to trigger the acquiring. Incertain embodiments, performing the at least one test on the one or moreUUTs may include generating a stimulus signal. The stimulus signalstimulates the UUT, and the signal from the UUT may thus be or include aresponse signal. In other words, the acquired signal may be in responseto the stimulus signal, and thus may be a response signal. Accordingly,in some embodiments, the leading edge of the digital pulse may besynchronized to the initiation of the stimulus signal. Alternatively, inother embodiments, the leading edge of the digital pulse may be delayedfor a time period from initiation of the stimulus signal, where the timeperiod may be determined by or correspond to elapsed time betweeninitiating an initial stimulus signal and receiving an initial responsesignal. In other words, the (trigger) pulse may be delayed to adjust fora representative latency between sending a stimulus signal and receivinga response to the stimulus signal, where, e.g., the representativelatency may be based on an actual latency in an initial test (whereinthe initial stimulus signal is sent, and the initial response signal isreceived) and may be characteristic of latencies regarding the at leastone test on the one or more UUTs.

In yet another embodiment, the acquiring of the response signal may beinitiated by the trailing edge of the digital pulse. The pulse width ofthe digital pulse may be a time period from initiation of the stimulussignal, where the time period may be determined by elapsed time betweeninitiating an initial stimulus signal and receiving an initial responsesignal. In other words, the digital pulse may begin when the stimulussignal is initiated (or generated), and may trigger the acquiring oncethe expected latency period has elapsed, per the pulse width, where thepulse width is based on the above mentioned initial test (with theinitial stimulus and initial response signal).

In certain embodiments, performing the at least one test on the one ormore UUTs may include performing an initial test of the at least onetest on an initial UUT of the one or more UUTs. The initial UUT may berepresentative of the one or more UUTs. To perform the initial test, astimulus signal may be generated, where the stimulus signal stimulatesthe initial UUT and an initial response signal may be acquired form theinitial UUT. A (or the) reference signal may be derived, where derivingthe reference signal may include removing distortions from the initialresponse signal. The reference signal may be stored for subsequentretrieval, and the initial response signal may be analyzed with respectto the reference signal. In some embodiments, the reference signal maybe one of a plurality of reference signals. In such embodiments, thereference signal may be retrieved based on determining one or morecharacteristics of the test (currently being performed, e.g., based on atest ID), the signal (transmitted from the UUT currently being tested ofthe at least one UUT), or, even the UUT (currently being tested) itself.In other words, the one or more characteristics may be determined, andthe (appropriate) reference signal retrieved based on the determining.

Thus, in some embodiments, the at least one test may include a pluralityof tests. In some of these embodiments, the reference signal may be oneof a plurality of reference signals. Each respective reference signalmay correspond to a respective test of the plurality of tests. Theplurality of tests may be performed on a first UUT of the one or moreUUTs. For each respective test of the plurality of tests a respectivereference signal of the plurality of reference signals may be determinedand a respective signal from the first UUT may be acquired.Additionally, the respective reference signal of the plurality ofreference signals may be retrieved. The respective signal may beanalyzed with respect to the respective reference signal.

In some embodiments, the one or more UUTs may include a plurality ofUUTs. In some of these embodiments, a first test may be performed oneach UUT of the plurality of UUTs. For each respective UUT of theplurality of UUTs, a respective signal from the respective UUT may beacquired. Additionally, a reference signal may be retrieved, e.g., fromstorage, possibly over a network. The respective signal may be analyzedwith respect to the reference signal.

In yet further embodiments, the reference signal may be one of aplurality of reference signals, the at least one test may include aplurality of tests, and the one or more UUTs may include a plurality ofUUTs. In such embodiments, each respective reference signal maycorrespond to a respective test of the plurality of tests and for eachtest of the plurality of tests a respective reference signal may bedetermined. Then, for each test of the plurality of tests for eachrespective UUT of the plurality of UUTs, a respective signal may beacquired from a respective UUT. Additionally, a respective referencesignal may be retrieved and the respective signal may be analyzed withrespect to the respective reference signal.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredin conjunction with the following drawings, in which:

FIG. 1 illustrates a flow chart for an RF signal processing method,according to the prior art;

FIG. 2A illustrates a computer system, according to an embodiment of theinvention;

FIG. 2B illustrates a network system, according to one embodiment;

FIG. 3A illustrates a test system, according to one embodiment;

FIG. 3B illustrates another system, according to one embodiment;

FIG. 4 illustrates an RF test system, according to one embodiment;

FIG. 5 illustrates a method for performing a test, according to oneembodiment; and

FIG. 6 illustrates a digital pulse signal, according to one embodiment.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION Definitions and Conventions

Unit Under Test (UUT)—A physical device or component that is beingtested.

Memory Medium—Any of various types of memory devices or storage devices.The term “memory medium” is intended to include an installation medium,e.g., a CD-ROM, floppy disks 104, or tape device; a computer systemmemory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM,Rambus RAM, etc.; or a non-volatile memory such as a magnetic media,e.g., a hard drive, or optical storage. The memory medium may compriseother types of memory as well, or combinations thereof. In addition, thememory medium may be located in a first computer in which the programsare executed, or may be located in a second different computer whichconnects to the first computer over a network, such as the Internet. Inthe latter instance, the second computer may provide programinstructions to the first computer for execution. The term “memorymedium” may include two or more memory mediums which may reside indifferent locations, e.g., in different computers that are connectedover a network.

Carrier Medium—a memory medium as described above, as well as signalssuch as electrical, electromagnetic, or digital signals, conveyed via acommunication medium such as a bus, network and/or a wireless link.

Acquisition—refers to the acquiring of analog signals and converting theanalog signals to digital data, e.g., bits.

Digital Signal—refers to a waveform that switches between two voltagelevels representing the two states of a Boolean value (0 and 1).

Digital Pulse—refers to one cycle of a digital signal, i.e., the switchfrom a low voltage level (Boolean 0) to a higher voltage level(Boolean 1) and the switch back to the low voltage level (Boolean 0).

Leading Edge of Digital Pulse—refers to the transition from a lowvoltage level (Boolean 0) to a higher voltage level (Boolean 1).

Trailing Edge of Digital Pulse—refers to the transition from a highervoltage level (Boolean 1) to a low voltage level (Boolean 0).

Pulse Width—refers to the elapsed time between the leading edge andtrailing edge of a digital pulse.

I/Q Data—I/Q data is a translation of amplitude and phase data from aPolar coordinate system to a Cartesian coordinate system. For example,the mathematical equation representing a sine wave can be expressed asin equation 1, where A_(c) represents amplitude of the sine wave, f_(c)represents the frequency of the sine wave, and φ represents the phase.

A _(c) sin(2πf _(c) t+φ)  (1)

In Polar coordinates, the sine wave can be represented in terms of themagnitude (amplitude), M(t), and phase, φ(t), at any instant in time. Totransform to Cartesian coordinates, equations 2 and 3 may be used todetermine the I/Q data.

I(t)=M(t)cos(φ(t))  (2)

Q(t)=M(t)sin(φ(t))  (3)

Power Edge Trigger—The power, P(t), of the I/Q data may be calculatedusing equation 4.

Q(t)=I ² +Q ²  (4)

When plotted, P(t) will have a rising edge with a positive slope and atrailing edge with a negative slope. Edge detection may be used todetect either the rising edge or trailing edge of the power of the I/Qdata and signal acquisition may be triggered from either edge.

Software Trigger—refers to a trigger to start an acquisition that isinitiated via software. The software may be of any form, including, butnot limited to, a graphical data flow program.

Correlation Methods—refers to a measurement of the similarity betweentwo signals. Methods include auto-correlation and cross-correlation.

Auto-correlation—refers to the correlation of a times series withitself.

Cross-correlation—refers to the measurement of the similarity betweentwo time series.

Carrier Signal—refers to a waveform, usually sinusoidal, that modulatesan input signal for the purpose of conveying information aselectromagnetic waves, in general, at a higher frequency that the inputsignal. A carrier signal is also referred to as a carrier.

Constellation—describes the I versus Q plot of the input signal.

Valid angle in the Constellation—refers to points in the IQ plane wherethe transmitter transmits at a known angular position for standardmodulation techniques.

Programmable Hardware Element—includes various types of programmablehardware, reconfigurable hardware, programmable logic, orfield-programmable devices (FPDs), such as one or more FPGAs (FieldProgrammable Gate Arrays), or one or more PLDs (Programmable LogicDevices), such as one or more Simple PLDs (SPLDs) or one or more ComplexPLDs (CPLDs), or other types of programmable hardware. A programmablehardware element may also be referred to as “reconfigurable logic”.

Medium—includes one or more of a memory medium, carrier medium, and/orprogrammable hardware element; encompasses various types of mediums thatcan either store program instructions/data structures or can beconfigured with a hardware configuration program.

Multiprocessor System—a computer system that includes multipleprocessing elements, i.e., processors, processing cores, or evennetworked computers, that may operate in a coordinated manner to executeprogram instructions concurrently.

Concurrently—a manner of performing actions or processes such that atleast a portion of the (concurrent) processes overlap in time, e.g., atleast one of the processes executes at least one iteration while anotherprocess executes an iteration. Concurrence, as used herein, may beaccomplished in any of multiple ways, including through the use ofsingle processor systems, e.g., via multi-threading, time-slices, etc.,or multiprocessor (or multicore) systems, as well as any other techniquefor processing functions at the same time.

Program—the term “program” is intended to have the full breadth of itsordinary meaning The term “program” includes 1) a software program whichmay be stored in a memory and is executable by a processor or 2) ahardware configuration program useable for configuring a programmablehardware element.

Software Program—the term “software program” is intended to have thefull breadth of its ordinary meaning, and includes any type of programinstructions, code, script and/or data, or combinations thereof, thatmay be stored in a memory medium and executed by a processor. Exemplarysoftware programs include programs written in text-based programminglanguages, such as C, C++, Pascal, Fortran, Cobol, Java, assemblylanguage, etc.; graphical programs (programs written in graphicalprogramming languages); assembly language programs; programs that havebeen compiled to machine language; scripts; and other types ofexecutable software. A software program may comprise two or moresoftware programs that interoperate in some manner.

Hardware Configuration Program—a program, e.g., a netlist or bit file,that can be used to program or configure a programmable hardwareelement.

Graphical Program—A program comprising a plurality of interconnectednodes or icons, wherein the plurality of interconnected nodes or iconsvisually indicate functionality of the program.

Data Flow Graphical Program (or Data Flow Diagram)—A graphical programor diagram comprising a plurality of interconnected nodes, wherein theconnections between the nodes indicate that data produced by one node isused by another node.

Graphical User Interface—this term is intended to have the full breadthof its ordinary meaning. The term “graphical user interface” is oftenabbreviated to “GUI”. A GUI may comprise only one or more input GUIelements, only one or more output GUI elements, or both input and outputGUI elements.

The following provides examples of various aspects of GUIs. Thefollowing examples and discussion are not intended to limit the ordinarymeaning of GUI, but rather provide examples of what the term “graphicaluser interface” encompasses:

A GUI may comprise a single window, panel, or dialog box having one ormore GUI Elements, or may comprise a plurality of individual GUIElements (or individual windows each having one or more GUI Elements),wherein the individual GUI Elements or windows may optionally be tiledtogether.

Graphical User Interface Element—an element of a graphical userinterface, such as for providing input or displaying output. Exemplarygraphical user interface elements include input controls and outputindicators.

Input Control—a graphical user interface element for providing userinput to a program. Exemplary input controls include buttons, checkboxes, input text boxes, knobs, sliders, etc.

Output Indicator—a graphical user interface element for displayingoutput from a program. Exemplary output indicators include charts,graphs, gauges, output text boxes, numeric displays, etc. An outputindicator is sometimes referred to as an “output control”.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

Measurement Device—includes instruments, data acquisition devices, smartsensors, and any of various types of devices that are operable toacquire and/or store data from a UUT. A measurement device may alsooptionally be further operable to analyze or process the acquired orstored data. Examples of a measurement device include an instrument,such as a traditional stand-alone “box” instrument, a computer-basedinstrument (instrument on a card) or external instrument, a dataacquisition card, a device external to a computer that operatessimilarly to a data acquisition card, a smart sensor, one or more DAQ ormeasurement cards or modules in a chassis, an image acquisition device,such as an image acquisition (or machine vision) card (also called avideo capture board) or smart camera, a motion control device, a robothaving machine vision, and other similar types of devices. Exemplary“stand-alone” instruments include oscilloscopes, multimeters, signalanalyzers, arbitrary waveform generators, spectroscopes, and similarmeasurement, test, or automation instruments.

A measurement device may be further operable to perform controlfunctions, e.g., in response to analysis of the acquired or stored data.For example, the measurement device may send a control signal to anexternal system, such as a motion control system or to a sensor, inresponse to particular data. A measurement device may also be operableto perform automation functions, i.e., may receive and analyze data, andissue automation control signals in response.

User Equipment (UE) (or “UE Device”)—any of various types of computersystems devices which are mobile or portable and which performs wirelesscommunications, such as mobile wireless devices. Examples of UE devicesinclude mobile telephones (e.g., cellular telephones (“cell phones”)) orsmart phones (e.g., iPhone™, Android™-based phones), portable gamingdevices (e.g., Nintendo DS™, PlayStation Portable™, Gameboy Advance™,iPod™), laptops, tablets (e.g., iPad™, Android™-based tablets), PDAs,portable Internet devices, music players, data storage devices, or otherhandheld devices, etc. In general, the term “UE” or “UE device” can bebroadly defined to encompass any electronic, computing, and/ortelecommunications device (or combination of devices) which is easilytransported by a user and capable of wireless communication.

FIG. 2A: Computer System

FIG. 2A illustrates a computer system 82 configured to implementembodiments of the present invention. More specifically, the computersystem 82 may be configured to execute one or more programs, e.g., oneor more graphical data flow programs, to execute unit testing andanalysis using a stored reference signal as described below in detail.

As shown in FIG. 2A, the computer system 82 may include a displaydevice. In some embodiments, the computer system 82 may be configured todisplay the (possibly graphical) program as the program is createdand/or executed. The display device may also be configured to display agraphical user interface or front panel of the program during executionof the program. The graphical user interface may comprise any type ofgraphical user interface, e.g., depending on the computing platform.

The computer system 82 may include at least one memory medium on whichone or more computer programs or software components according to oneembodiment of the present invention may be stored. The memory may becoupled to one or more processors and store program instructionsexecutable by the one or more processors. For example, the memory mediummay store one or more programs, e.g., graphical programs, which areexecutable to perform embodiments of the methods described herein.Additionally, the memory medium may store a programming developmentenvironment application used to create and/or execute such programs. Thememory medium may also store operating system software, as well as othersoftware for operation of the computer system. Various embodimentsfurther include receiving or storing instructions and/or dataimplemented in accordance with the foregoing description upon a carriermedium.

FIG. 2B: Computer Network

FIG. 2B illustrates a system including a first computer system 82 thatis coupled to a second computer system 90. The computer system 82 may becoupled via a network 84 (or a computer bus) to the second computersystem 90. The computer systems 82 and 90 may each be any of varioustypes, as desired. The network 84 can also be any of various types,including a LAN (local area network), WAN (wide area network), theInternet, or an Intranet, among others. The computer systems 82 and 90may execute programs, e.g., one or more graphical programs, in adistributed fashion. For example, computer 82 may execute a firstportion of the block diagram of a graphical program and computer system90 may execute a second portion of the block diagram of the graphicalprogram. As another example, computer 82 may display the graphical userinterface of a graphical program and computer system 90 may execute theblock diagram of the graphical program.

In one embodiment, the graphical user interface of the program may bedisplayed on a display device of the computer system 82, and the blockdiagram may execute on a device coupled to the computer system 82. Thedevice may include a programmable hardware element and/or may include aprocessor and memory medium which may execute a real time operatingsystem. In one embodiment, the program may be downloaded and executed onthe device. For example, an application development environment withwhich the program is associated may provide support for downloading aprogram for execution on the device in a real time system. It should benoted that while various embodiments are described herein in terms of agraphical program implementation, any other types of programs orprogramming technologies may be used as desired

FIGS. 3A-3B: Exemplary Systems

Embodiments of the present invention may be involved with performingtest and/or measurement functions; controlling and/or modelinginstrumentation or industrial automation hardware; modeling andsimulation functions, e.g., modeling or simulating a device or productbeing developed or tested, etc. Exemplary test applications where thegraphical program may be used include hardware-in-the-loop testing andrapid control prototyping, among others.

However, it is noted that embodiments of the present invention can beused for a plethora of applications and is not limited to the aboveapplications. In other words, applications discussed in the presentdescription are exemplary only, and embodiments of the present inventionmay be used in any of various types of systems. Thus, embodiments of thesystem and method of the present invention is configured to be used inany of various types of applications, including the control of othertypes of devices such as multimedia devices, video devices, audiodevices, telephony devices, Internet devices, etc., as well as generalpurpose software applications such as word processing, spreadsheets,network control, network monitoring, financial applications, games, etc.

FIG. 3A illustrates an exemplary instrumentation control system 100which may implement embodiments of the invention. The system 100comprises a host computer 82 which couples to one or more instruments.The host computer 82 may comprise a CPU, a display screen, memory, andone or more input devices such as a mouse or keyboard as shown. Thecomputer 82 may operate with the one or more instruments to analyze,measure, or control a unit under test (UUT) or process 150.

The one or more instruments may include a GPIB instrument 112 andassociated GPIB interface card 122, a data acquisition board 114inserted into or otherwise coupled with chassis 124 with associatedsignal conditioning circuitry 126, a VXI instrument 116, a PXIinstrument 118, a video device or camera 132 and associated imageacquisition (or machine vision) card 134, a motion control device 136and associated motion control interface card 138, and/or one or morecomputer based instrument cards 142, among other types of devices. Thecomputer system may couple to and operate with one or more of theseinstruments. The instruments may be coupled to the unit under test (UUT)or process 150, or may be coupled to receive field signals, typicallygenerated by transducers. The system 100 may be used in a dataacquisition and control application, in a test and measurementapplication, an image processing or machine vision application, aprocess control application, a man-machine interface application, asimulation application, or a hardware-in-the-loop validationapplication, among others.

FIG. 3B illustrates an exemplary industrial automation system 160 whichmay implement embodiments of the invention. The industrial automationsystem 160 may be similar to the instrumentation or test and measurementsystem 100 shown in FIG. 3A. Elements which are similar or identical toelements in FIG. 3A have the same reference numerals for convenience.The system 160 may comprise a computer 82 which couples to one or moredevices or instruments. The computer 82 may comprise a CPU, a displayscreen, memory, and one or more input devices such as a mouse orkeyboard as shown. The computer 82 may operate with the one or moredevices to perform an automation function with respect to a process ordevice 150, such as MMI (Man Machine Interface), SCADA (SupervisoryControl and Data Acquisition), portable or distributed data acquisition,process control, advanced analysis, or other control, among others.

The one or more devices may include a data acquisition board 114inserted into or otherwise coupled with chassis 124 with associatedsignal conditioning circuitry 126, a PXI instrument 118, a video device132 and associated image acquisition card 134, a motion control device136 and associated motion control interface card 138, a fieldbus device170 and associated fieldbus interface card 172, a PLC (ProgrammableLogic Controller) 176, a serial instrument 182 and associated serialinterface card 184, or a distributed data acquisition system, such asthe Fieldpoint system available from National Instruments, among othertypes of devices.

In the embodiments of FIGS. 3A and 3B above, one or more of the variousdevices may couple to each other over a network, such as the Internet.In one embodiment, the user operates to select a target device from aplurality of possible target devices for programming or configuration,e.g., using a graphical program. Thus the user may create a graphicalprogram on a computer and use (execute) the graphical program on thatcomputer or deploy the graphical program to a target device (for remoteexecution on the target device) that is remotely located from thecomputer and coupled to the computer through a network.

Graphical software programs which perform data acquisition, analysisand/or presentation, e.g., for measurement, instrumentation control,industrial automation, modeling, or simulation, such as in theapplications shown in FIGS. 4A and 4B, may be referred to as virtualinstruments (VIs).

FIG. 4: Exemplary RF System

FIG. 4 illustrates an exemplary RF test system 460 which may implementembodiments of the invention. The RF test system 460 may be similar tothe instrumentation or test and measurement system 100 shown in FIG. 3A.It should be noted that the RF signals may be of any type, including,but not limited to, non-Orthogonal Frequency-Division Multiplexing(non-OFDM) cellular standards, such as Wideband Code Division MultipleAccess (WCDMA), the Code Division Multiple Access 2000 family ofstandards (CDMA2K), and Global System for Mobile Communications—EnhancedData rates for GSM Evolution (GSM-EDGE), and OFDM cellular standardssuch as, Long Term Evolution (LTE), Worldwide Interoperability forMicrowave Access (WiMAX), and Wireless Local Area Network (WiLan).Elements which are similar or identical to elements in FIG. 3A have thesame reference numerals for convenience.

The system 460 may include a computer 82 which couples to one or moredevices or instruments. The computer 82 may include one or moreprocessors, a display screen, memory coupled to the one or moreprocessors, and one or more input devices such as a mouse or keyboard asshown. In one embodiment, the PXI chassis 418 may include one or more RFmeasurement cards, such as those made by National Instruments. The oneor more RF measurement cards may include a memory coupled to one or moreprocessors. Additionally, the chassis 418 may include a memory coupledto one or more processors. Further, the RF measurement cards may beconfigured to stimulate, or transmit signals to, one or more UUTs, suchas UE devices 414 a-414 d and also received signals from the one or moreUUTs. In some embodiments, one or more signals from the one or more UUTsmay be transmitted and received concurrently. In other embodiments, UEdevices 414 a-414 d may transmit waveforms types corresponding to anycellular standard, such as, but not limited to, WCDMA, CDMA2K, GSM-EDGE,LTE, and so forth.

It should be noted that a UE device may be any of various types ofcomputer systems devices which are mobile or portable and which performswireless communications, such as mobile wireless devices. Examples of UEdevices include mobile telephones (e.g., cellular telephones (“cellphones”) or smart phones, portable gaming devices, laptops, tablets,PDAs, portable Internet devices, music players, data storage devices, orother handheld devices, etc. In general, the term “UE” or “UE device”can be broadly defined to encompass any electronic, computing, and/ortelecommunications device (or combination of devices) which is easilytransported by a user and capable of wireless communication.

It should also be noted that any of the system components describedabove may be used in any combination to perform embodiments of themethod illustrated in FIG. 5 and described in detail below.

FIG. 5: Flowchart of a Method for Testing UUTs

FIG. 5 is a flowchart diagram of a method for implementing or performinga test process. The method shown in FIG. 5 may be used in conjunctionwith any of the computer systems or devices shown in the above Figures,among other devices. In various embodiments, some of the method elementsshown may be performed concurrently, in a different order than shown, ormay be omitted. Additional method elements may also be performed asdesired. As shown, this method may operate as follows.

In 510, at least one test on one or more UUTs may be performed. In someembodiments the at least one test may include a plurality of tests andthe one or more UUTs may include a plurality of UUTs. In otherembodiments, the at least one test may include at least one RF test. Insuch embodiments, the one or more UUTs may include one or more UEdevices, such as wireless mobile devices.

In 512, a signal may be acquired from a UUT of one or more UUTs. Asnoted above, in some embodiments, the one or more UUTs may be aplurality of UUTs and the signal may be acquired from a first UUT of theplurality of UUTs. It should be noted that the signal acquired from theUUT may be of any type, including, but not limited to RF signals such asthose used in cellular communication standards, such as WCDMA, CDMA2K,GSM-EDGE, LTE, and so forth.

In 514, a reference signal may be retrieved (e.g., from memory, possiblyover a network). The reference signal may be derived from a transmittedsignal that is characteristic of the UUT, or more generally, from atransmitted signal that is characteristic of the one or more UUTs. Insome embodiments, the reference signal may be one of a plurality ofreference signals, and may be selected or determined based on one ormore criteria. Accordingly, in some embodiments, retrieving thereference signal may include determining one or more characteristics ofthe test (currently being performed, e.g., based on a test ID), thesignal (transmitted from the UUT currently being tested of the at leastone UUT), or, even the UUT (currently being tested) itself, andselecting the reference signal based on the determining, e.g., based oninformation determined regarding the test, the signal, or the UUT. Insome embodiments where characteristics of the signal are determined, thecharacteristics may include the waveform type being transmitted, suchas, but not limited to, OFDM, non-OFDM, or TDMA. In other embodiments,the characteristics may include the cellular standard being used by theUUT, such as, but not limited to, WCDMA, CDMA2K, GSM-EDGE, LTE, WiMax,or WiLan. Other attributes or characteristics may be used as desired.

In some embodiments, an initial test of the at least one test may beperformed on an initial UUT of the one or more UUTs, where the initialUUT is representative of the one or more UUTs. To perform the initialtest, a stimulus signal may be generated, where the stimulus signalstimulates the initial UUT and an initial response signal may beacquired from the initial UUT.

A (or the) reference signal may be derived, where deriving the referencesignal may include removing distortions from the initial responsesignal. In one embodiment, the derivation may include removingdistortion from the initial signal. In other embodiments, such as thoseinvolving OFDM and non-OFDM signals, removing distortion may includedemodulating the initial signal. In embodiments involving TDMA signals,removing distortion may include both demodulating and re-modulating theinitial signal.

The reference signal may be stored for subsequent retrieval, and theinitial response signal may be analyzed with respect to the referencesignal. In some embodiments, the reference signal may be one of aplurality of reference signals. In such embodiments, the referencesignal may be retrieved based on determining one or more characteristicsof the test (currently being performed, e.g., based on a test ID), thesignal (transmitted from the UUT currently being tested of the at leastone UUT), or, even the UUT (currently being tested) itself. In otherwords, the one or more characteristics may be determined, and the(appropriate) reference signal retrieved based on the determining.

In some embodiments, a marker may be used to synchronize the signal thatmay be acquired to the reference signal. The marker, in certainembodiments, may include a digital pulse, a software trigger, a poweredge trigger, a correlation method such as cross-correlation, or someother form of signal synchronization.

In 516, the signal may be analyzed with respect to the reference signal.In certain embodiments, the analysis may include calculating metricssuch as EVM, Modulation Accuracy EVM, Code Domain Power, EVMQPSK, andother similar signal metrics. In certain embodiments, the analysis mayinclude use of the marker.

For example, a signal, m(n), may be acquired using a marker forsynchronization, and may be mathematically represented as shown inequation 5.

m(n+p ₀)=A _(n+p) ₀ e ^(j{α(n+p) ⁰ ^()+φ(n+p) ⁰ ^()+θ}) +Be ^(jβ)  (5)

In equation 5, A_(n) is the power (magnitude) of the signal, φ(n) is theangle error corresponding to the frequency offset in the carrier signal,θ is the angle error corresponding to the phase offset in the carriersignal, α(n) is the valid angle in the constellation, p₀ is thefractional time offset between signal generation and signal acquisitioncaused by trigger jitter, and Be^(jβ) represents the power offsetpresent in the acquired signal. Additionally, as shown in equation 6, Δωis the frequency offset in radians per sample, where,

φ(n)=Δω_(n)  (6)

The reference signal, r(n), that may be retrieved, may be mathematicallyrepresented as shown in equation 7.

r(n)=A _(n) e ^(jα(n))  (7)

The trigger jitter, p₀ may be estimated and removed using a combinationof alignment algorithms as known in the art. Once this jitter isremoved, equation 5 simplifies to equation 8.

m′(n)=A _(n) e ^(j{α(n)+φ(n)+θ}) +Be ^(jβ)  (8)

Now, the reference signal may be used to remove impairments in theacquired signal, such as carrier frequency offset (CFO), carrier phaseoffset (CPO), and power offset as shown in equation 9.

q(n)=∠m′(n) r*(n)=Δω_(n)+θ  (9)

The frequency offset, Δω, and the phase offset, θ, can then bedetermined using the least squares technique. The signal m″(n), shown inequation 10, is the signal m′(n) with the CFO and CPO removed.

m″(n)=A _(n) e ^(jα(n)) +Be ^(jβ)  (10)

The reference signal, r(n), may be employed to estimate and correct forthe power offset, Be^(jβ) present in the signal, m″ (n) as shown inequations 11-12.

$\begin{matrix}{{\hat{B}^{j\; \hat{\beta}}} = {\frac{1}{L}{\sum\limits_{n = 0}^{L - 1}\left( {{r(n)} - {m^{''}(n)}} \right)}}} & (11) \\{{m^{\prime\prime\prime}(n)} = {{m^{''}(n)} - {\hat{B}^{j\; \hat{\beta}}}}} & (12)\end{matrix}$

In equations 11-12, {circumflex over (B)}e^(j{circumflex over (β)})represents the estimated power offset and L is the length of theacquired signal. Finally, the EVM may be calculated using the referencecorrected signal, m′″(n), and the reference signal, r(n), as in equation13.

$\begin{matrix}{{EVM} = \sqrt{\frac{\sum\limits_{n = 0}^{L - 1}{{{m^{\prime\prime\prime}(x)} - {r(n)}}}^{2}}{L}}} & (13)\end{matrix}$

In some embodiments, as mentioned above, the at least one test maycomprise a plurality of tests, and for each respective test of theplurality of tests, a respective reference signal may be determined andretrieved. Accordingly, in one embodiment, for a first UUT of the one ormore UUTs, a plurality of tests may be performed for which a respectivereference signal is determined and retrieved for each respective test ofthe plurality of tests performed on the first UUT. In other embodimentswhere the one or more UUTs include a plurality of UUTs, the plurality oftests may be performed on the plurality of UUTs. Accordingly, arespective reference signal may be determined and retrieved for eachrespective test of the plurality of tests on a respective UUT. In otherwords, the same reference signal may be used for the same test repeatedfor different UUTs. Hence, in some embodiments, the retrieved referencesignal is respective to the test and may be independent of theparticular UUT being tested.

In 520, results of the performing the at least one test on the one ormore UUTs, where the results are useable to characterize the one or moreUUTs may be stored. It is envisioned that the storage of the results maybe any one of a variety of forms, but at least includes storing theresults to a memory. The storage may include transient storage such asRAM and display of results on a computer, such as computer system 82 ofFIG. 2A above. Additionally, storage may include a network system, suchas the network system described above in FIG. 2B. Accordingly, it isenvisioned that the results may be stored in a database on a server. Itis also envisioned, that in certain embodiments, the results may be usedfor other purposes in the manufacturing of the UUT, such as determiningwhether the UUT is within some specified quality control limit.

In certain embodiments, the at least one test may include at least oneradio frequency (RF) test. In one embodiment, the UUT may be a UEdevice, such as depicted in 414 a-414 d of FIG. 4. It should be notedthe term “UE” or “UE device” can be broadly defined to encompass anyelectronic, computing, and/or telecommunications device (or combinationof devices) which is easily transported by a user and capable ofwireless communication, such as mobile wireless devices. In suchembodiments, the RF tests may be based on any cellular standard,including, but not limited to, WCDMA, CDMA2K, GSM-EDGE, LTE, WiMax, orWiLan. In certain embodiments, the reference signal may be stored in amemory on the computer system 82, computer system 90, or on a memory ofany of various measurement hardware, such as PXI chassis 416.

For example, where the UUTs include mobile wireless devices, at leastone RF test may be performed on one or more UUTs, including one or moremobile wireless devices. An RF signal may be acquired from a UUT, e.g.,a mobile wireless device, of the one or more UUTs. An RF referencesignal may be retrieved, where the RF reference signal is derived from atransmitted RF signal that is characteristic of the UUT. The RF signalmay be analyzed with respect to the RF reference signal. The results ofperforming the at least one RF test on the one or more UUTs, where theresults are useable to characterize the one or more UUTs, may be stored.

It is envisioned that in certain embodiments, regarding exemplaryembodiments of the systems disclosed herein, reference signalscorresponding to each cellular standard and signal type may be derivedand stored in a database. In such embodiments, when a test is performedfor a given cellular standard, the reference signal may be retrievedfrom the database of reference signals based on the cellular standardand/or signal type, although other bases for the retrievals may be usedas desired, e.g., based on test IDs, etc. In certain embodiments, thedatabase may be accessed over a network, such as that described in FIG.2B above. Accordingly, in some embodiments, the database of referencesignals may be stored on a server.

FIG. 6: Exemplary Marker

FIG. 6 illustrates an exemplary marker 600. In one embodiment, themarker may be or include a digital pulse 610, as illustrated in FIG. 6.The digital pulse 610 has a leading edge 614, a pulse width 616, and atrailing edge 618. In one embodiment, an edge of the digital pulse 610may initiate or trigger the acquiring of the response signal. In certainembodiments, performing the at least one test on the one or more UUTsmay include generating a stimulus signal. The stimulus signal stimulatesthe UUT. The signal from the UUT may thus be or include a responsesignal, where the response signal is in response to the stimulus signal.In other words, the acquired signal may be in response to the stimulussignal, and thus may be a response signal.

Accordingly, in some embodiments, the leading edge 614 of the digitalpulse may be synchronized to the initiation of the stimulus signal. Inother embodiments, the leading edge 614 may be delayed for a time periodfrom the initiation of the stimulus signal by delay 602. The time periodof the delay 602 may be determined by or correspond to the elapsed timebetween initiating an initial stimulus signal and receiving an initialresponse signal. In other words, the (trigger) pulse may be delayed toadjust for a representative latency between sending a stimulus signaland receiving a response to the stimulus signal, where, e.g., therepresentative latency may be based on an actual latency in an initialtest (wherein the initial stimulus signal is sent, and the initialresponse signal is received) and may be characteristic of latenciesregarding the at least one test on the one or more UUTs.

In yet another embodiment, the trailing edge 618 of the digital pulse610 may initiate or trigger the acquiring of the response signal. Thepulse width 616 of the marker may be a time period from initiation ofthe stimulus signal, where the time period may be determined by theelapsed time between initiating an initial stimulus signal and receivingan initial response signal. In other words, the digital pulse may beginwhen the stimulus signal is initiated (or generated), and may triggerthe acquiring once the expected latency period has elapsed, per thepulse width, where the pulse width is based on the above mentionedinitial test (with the initial stimulus and initial response signal).

In certain embodiments, the marker may be used to synchronize theacquired signal to the reference signal. Additionally, while a digitalpulse marker is described in detail herein, it is envisioned that otherforms of triggering and synchronization may be used. Hence, in certainembodiments it is envisioned that the marker may be a software trigger.In other embodiments, the marker may be a power edge trigger. In yetother embodiments, the marker may include a correlation method such ascross-correlation.

It should be noted that while specific embodiments have been describedand disclosed herein, it is intended that any features of anyembodiments described herein may be combined or used together asdesired, and further, may be implemented via any embodiments of thesystems disclosed herein, or variants thereof.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

We claim:
 1. A non-transitory computer accessible memory medium thatstores program instructions for testing units under test (UUTs), whereinthe program instructions are executable to implement: performing atleast one test on one or more UUTs, comprising: acquiring a signal froma UUT of the one or more UUTs; retrieving a reference signal, whereinthe reference signal is derived from a transmitted signal that ischaracteristic of the UUT; and analyzing the signal with respect to thereference signal; and storing results of said performing the at leastone test on the one or more UUTs, wherein the results are useable tocharacterize the one or more UUTs.
 2. The non-transitory computeraccessible memory medium of claim 1, wherein said acquiring issynchronized to the reference signal via a marker.
 3. The non-transitorycomputer accessible memory medium of claim 2, wherein the marker is adigital pulse and wherein said acquiring the signal is initiated by anedge of the digital pulse.
 4. The non-transitory computer accessiblememory medium of claim 3, wherein said performing the at least one teston the one or more UUTs comprises: generating a stimulus signal, whereinthe stimulus signal stimulates the UUT, wherein the signal from the UUTcomprises a response signal, and wherein the response signal is inresponse to the stimulus signal.
 5. The non-transitory computeraccessible memory medium of claim 4, wherein the leading edge of thedigital pulse is synchronized to initiation of the stimulus signal. 6.The non-transitory computer accessible memory medium of claim 4, whereinthe leading edge of the digital pulse is delayed for a time period frominitiation of a stimulus signal, and wherein the time period isdetermined by elapsed time between initiating an initial stimulus signaland receiving an initial response signal.
 7. The non-transitory computeraccessible memory medium of claim 4, wherein the marker is a digitalpulse, wherein said acquiring a response signal is initiated by atrailing edge of the digital pulse, wherein the pulse width of thedigital pulse is a time period from initiation of the stimulus andwherein the time period is determined by elapsed time between initiatingan initial stimulus signal and receiving an initial response signal. 8.The non-transitory computer accessible memory medium of claim 2, whereinthe marker comprises one of the following: a digital pulse; a softwaretrigger, a power edge trigger; or a correlation method.
 9. Thenon-transitory computer accessible memory medium of claim 1, whereinsaid performing the at least one test on the one or more UUTs comprises:performing an initial test of the at least one test on an initial UUT ofthe one or more UUTs, wherein the initial UUT is representative of theone or more UUTs, comprising: generating a stimulus signal, wherein thestimulus signal stimulates the initial UUT; acquiring an initialresponse signal from the initial UUT; deriving the reference signal,wherein deriving the reference signal comprises removing distortionsfrom the initial response signal; storing the reference signal forsubsequent retrieval; and analyzing the initial response signal withrespect to the reference signal.
 10. The non-transitory computeraccessible memory medium of claim 1, wherein the reference signal is oneof a plurality of reference signals, wherein said retrieving comprises:determining one or more characteristics of the test, the signal, or theUUT; and selecting the reference signal based on said determining. 11.The non-transitory computer accessible memory medium of claim 1, whereinthe at least one test comprises a plurality of tests; wherein thereference signal is one of a plurality of reference signals, eachrespective reference signal corresponding to a respective test of theplurality of tests; and wherein said performing at least one test on theone or more UUTs comprises: performing the plurality of tests on a firstUUT of the one or more UUTs, comprising: for each respective test of theplurality of tests: determining a respective reference signal of theplurality of reference signals for the respective test; acquiring arespective signal from the first UUT; retrieving the respectivereference; and analyzing the respective signal with respect to therespective reference signal.
 12. The non-transitory computer accessiblememory medium of claim 1, wherein the one or more UUTs comprise aplurality of UUTs, and wherein said performing at least one test on theone or more UUTs comprises: performing a first test on each UUT of theplurality of UUTs, comprising: for each respective UUT of the pluralityof UUTs: acquiring a respective signal from the respective UUT;retrieving the reference signal; and analyzing the respective signalwith respect to the reference signal.
 13. The non-transitory computeraccessible memory medium of claim 1, wherein the at least one testcomprises a plurality of tests; wherein the reference signal is one of aplurality of reference signals, each respective reference signalcorresponding to a respective test of the plurality of tests; whereinthe one or more UUTs comprise a plurality of UUTs; and wherein saidperforming at least one test on the one or more UUTs comprises:performing the plurality of tests on the plurality of UUTs, comprising:for each respective test of the plurality of tests: determining arespective reference signal of the plurality of reference signals forthe respective test; and for each respective UUT of the plurality ofUUTs:  acquiring a respective signal from the respective UUT; retrieving the respective reference signal of the plurality ofreference signals; and  analyzing the respective signal with respect tothe respective reference signal.
 14. The non-transitory computeraccessible memory medium of claim 1, wherein said performing at leastone test on the one or more UUTs comprises performing at least one radiofrequency (RF) test on at least one mobile wireless device.
 15. A systemfor a test process, the system comprising: a processor; and a memory,coupled to the processor, wherein the memory stores program instructionsexecutable by the processor to implement: performing at least one teston one or more UUTs, comprising: acquiring a signal from a UUT of theone or more UUTs; retrieving a reference signal, wherein the referencesignal is derived from a transmitted signal that is characteristic ofthe UUT; and analyzing the signal with respect to the reference signal;and storing results of said performing the at least one test on the oneor more UUTs, wherein the results are useable to characterize the one ormore UUTs.
 16. The system of claim 15, wherein said acquiring issynchronized to the reference signal via a marker.
 17. The system ofclaim 16, wherein the marker is a digital pulse and wherein saidacquiring the signal is initiated by an edge of the digital pulse. 18.The system of claim 17, wherein said performing the at least one test onthe one or more UUTs comprises: generating a stimulus signal, whereinthe stimulus signal stimulates the UUT, wherein the signal from the UUTcomprises a response signal, and wherein the response signal is inresponse to the stimulus signal.
 19. The system of claim 18, wherein theleading edge of the digital pulse is synchronized to initiation of thestimulus signal.
 20. The system of claim 18, wherein the leading edge ofthe digital pulse is delayed for a time period from initiation of astimulus signal, and wherein the time period is determined by elapsedtime between initiating an initial stimulus signal and receiving aninitial response signal.
 21. The system of claim 18, wherein the markeris a digital pulse, wherein said acquiring a response signal isinitiated by a trailing edge of the digital pulse, wherein the pulsewidth of the digital pulse is a time period from initiation of thestimulus and wherein the time period is determined by elapsed timebetween initiating an initial stimulus signal and receiving an initialresponse signal.
 22. The system of claim 16, wherein the markercomprises one of the following: a digital pulse; a software trigger, apower edge trigger; or a correlation method.
 23. The system of claim 15,wherein said performing the at least one test on the one or more UUTscomprises: performing an initial test of the at least one test on aninitial UUT of the one or more UUTs, wherein the initial UUT isrepresentative of the one or more UUTs, comprising: generating astimulus signal, wherein the stimulus signal stimulates the initial UUT;acquiring an initial response signal from the initial UUT; deriving thereference signal, wherein deriving the reference signal comprisesremoving distortions from the initial response signal; storing thereference signal for subsequent retrieval; and analyzing the initialresponse signal with respect to the reference signal.
 24. The system ofclaim 15, wherein the reference signal is one of a plurality ofreference signals, wherein said retrieving comprises: determining one ormore characteristics of the test, the signal, or the UUT; and selectingthe reference signal based on said determining.
 25. The system of claim15, wherein the at least one test comprises a plurality of tests;wherein the reference signal is one of a plurality of reference signals,each respective reference signal corresponding to a respective test ofthe plurality of tests; and wherein said performing at least one test onthe one or more UUTs comprises: performing the plurality of tests on afirst UUT of the one or more UUTs, comprising: for each respective testof the plurality of tests: determining a respective reference signal ofthe plurality of reference signals for the respective test; acquiring arespective signal from the first UUT; retrieving the respectivereference; and analyzing the respective signal with respect to therespective reference signal.
 26. The system of claim 15, wherein the oneor more UUTs comprise a plurality of UUTs, and wherein said performingat least one test on the one or more UUTs comprises: performing a firsttest on each UUT of the plurality of UUTs, comprising: for eachrespective UUT of the plurality of UUTs: acquiring a respective signalfrom the respective UUT; retrieving the reference signal; and analyzingthe respective signal with respect to the reference signal.
 27. Thesystem of claim 15, wherein the at least one test comprises a pluralityof tests; wherein the reference signal is one of a plurality ofreference signals, each respective reference signal corresponding to arespective test of the plurality of tests; wherein the one or more UUTscomprise a plurality of UUTs; and wherein said performing at least onetest on the one or more UUTs comprises: performing the plurality oftests on the plurality of UUTs, comprising: for each respective test ofthe plurality of tests: determining a respective reference signal of theplurality of reference signals for the respective test; and for eachrespective UUT of the plurality of UUTs:  acquiring a respective signalfrom the respective UUT;  retrieving the respective reference signal ofthe plurality of reference signals; and  analyzing the respective signalwith respect to the respective reference signal.
 28. The system of claim15, wherein said performing at least one test on the one or more UUTscomprises performing at least one radio frequency (RF) test on at leastone mobile wireless device.
 29. A computer-implemented method forperforming testing on units under test (UUTs), comprising: performing atleast one test on one or more UUTs, comprising: acquiring a signal froma UUT of the one or more UUTs; retrieving a reference signal, whereinthe reference signal is derived from a transmitted signal that ischaracteristic of the UUT; and analyzing the signal with respect to thereference signal; and storing results of said performing the at leastone test on the one or more UUTs, wherein the results are useable tocharacterize the one or more UUTs.
 30. A non-transitory computeraccessible memory medium that stores program instructions for RF testingof units under test (UUTs), wherein the program instructions areexecutable to implement: performing at least one RF test on one or moreUUTs, wherein the UUTs comprise mobile wireless devices, comprising:acquiring an RF signal from a UUT of the one or more UUTs; retrieving anRF reference signal, wherein the RF reference signal is derived from atransmitted RF signal that is characteristic of the UUT; and analyzingthe RF signal with respect to the RF reference signal; and storingresults of said performing the at least one RF test on the one or moreUUTs, wherein the results are useable to characterize the one or moreUUTs.